


Joined

by Soulstoned



Category: Voltron: Legendary Defender
Genre: Accidental Knotting, Accidental Oviposition, Alien Biology, Bottom Shiro (Voltron), First Time, M/M, Mpreg, Tentacle Dick, Xeno
Language: English
Status: Completed
Published: 2020-03-01
Updated: 2020-03-01
Packaged: 2021-02-27 22:41:22
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 3,767
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/22973446
Author URL: https://archiveofourown.org/users/Soulstoned/pseuds/Soulstoned
Summary: Keith and Shiro have been dating for a month and are finally ready to go all the way. Keith's alien side makes itself known and they both get a little bit more than they bargained for.
Relationships: Keith/Shiro (Voltron)
Comments: 13
Kudos: 164
Collections: Sheithlentines 2020





	Joined

**Author's Note:**

  * For [Neurotenical (ThatAcePaladin)](https://archiveofourown.org/users/ThatAcePaladin/gifts).



Keith walks Shiro to his door after an evening of hoverbike racing through the desert. It's been a month since the night they first confessed their feelings to each other and had their first kiss, but they still haven't gotten past kissing. Keith is trying not to be impatient. He has his own reasons for wanting to take things slow, so the fact that Shiro is on the same page should feel like a blessing. Instead, each night that passes with just a kiss on the doorstep before going their separate ways is an exercise in frustration.

Keith leans into it as Shiro bends down to kiss him goodnight. He turns to leave as Shiro keys in the code to open his door, but is stopped by Shiro's hand grabbing his. "Wait, would you like to come in?" Shiro asks, trying to stay casual and fight back a slight blush. "Only if you want to, of course. No pressure," he adds quickly.

"Yeah, I'd love to," Keith says with a smile, following Shiro into his room. Nerves picking up as his mind races through what this might mean.

As soon as the door closes behind him he's backed up against it as Shiro bends down to capture his mouth in another scorching kiss. "I've been wanting to do that all evening," he says as he pulls back slightly, still caging Keith against the door.

"What was stopping you?" Keith asks as he wraps his arms around his neck to drag him back down.

"I want to take my time with you," Shiro says, bringing his hand up to cup Keith's cheek before allowing himself to be pulled into another kiss, this one slower and more gentle than the first.

"I hope you know what you're getting into," Keith says as his hands trail downward, coming to rest at the small of Shiro's back, not wanting to press further without permission no matter how hard that is starting to get.

"Do you want to lay down and see where this goes?" Shiro asks.

Keith doesn't know why he's so nervous. It isn't like he's never had sex before, but that was before he spent years in space as his body changed, mostly in ways that remain unseen when fully clothed.

Looking up at Shiro and seeing the tenderness in his gaze, makes him want to do this right. Shiro deserves to be romanced properly, and not blindsided by what he's about to see.

"Yeah, that sounds good, but there's something I need to warn you about first," Keith says, kicking off his shoes and allowing himself to be led over to the bed.

"What is it?" Shiro asks, pulling away slightly to sit on the edge of the bed, looking up at Keith expectantly.

Keith sighs and nervously runs his fingers through his hair. "Okay, you know how I'm half-galra?" 

Shiro looks up at him in amusement. "Yes, I think that has been established."

"Okay, well, um. There isn't an easy way to say this… " Keith pauses, unsure how to continue but knowing he needs to get the words out before this goes any further.

Shiro's amusement turns to concern as Keith continues to falter. "Hey, whatever it is, we'll get through it, you can tell me."

"My dick is weird."

"Is that it?" Shiro asks, relaxing now that he knows it isn't anything serious.

"I don't know if you understand _how_ weird. I mean, it was a little different from most guys before, but when I hit that growth spurt in the quantum abyss, it changed more than the rest of me, and I just want you to know what you're getting into…oof" Keith is interrupted from his spiraling by Shiro pulling him down onto the bed.

"I don't care what kind of dick you have, or even if you have one at all, I just want you," Shiro says, pulling Keith into his lap to pick up where they left off with the kissing.

"You have me," Keith says with a smile, allowing himself to be guided to lie down in the center of Shiro's bed.

They lie down face to face on top of the covers, wrapping their arms around each other as they continue to kiss. Keith slides his hands beneath Shiro's shirt eliciting a gasp as his fingers brush over scarred skin without the barrier of fabric.

Shiro sits up and yanks his shirt off before sinking back down against the bed. Keith explores every inch of newly bared skin, mapping out scars with his fingertips and determined to remember every detail of this night, just in case it never happens again. 

He has appreciated the sight of Shiro shirtless many times in the past, but this is the first time he's been able to touch and he takes full advantage of the opportunity, squeezing and stroking and dipping down to take a sensitive nipple into his mouth, gently rubbing the other with his fingertips so it won't feel neglected.

Keith reluctantly pulls back long enough to remove his own shirt, enjoying the hungry look Shiro gives him as he does so.

"See something you like?" he asks with a laugh as he tosses his shirt to the side. 

Shiro responds by pinning him to the bed and kissing down the side of his face and neck, stopping on the large scar on his shoulder, a souvenir from his Blade of Marmora trial. The skin to skin contact and the feeling of being pinned down by the weight above him feels like heaven. Like every wet dream he has ever had in one.

They continue like that, slow and gentle, exploring each other's bodies as clothes come off piece by piece, barely coming apart for air until finally Keith is down to just his boxers while Shiro lounges back against the pillows, naked and wanting.

It's the moment of truth. Keith closes his eyes so he doesn't have to see Shiro's face as he quickly kicks off his boxers. He isn't bracing for rejection exactly, Shiro is far too polite for that. It’s hesitation he fears. Evidence that Shiro would rather be with someone less alien.

He feels a hand on his hip and opens his eyes and sees Shiro, looking at him in awe, cock still hard between them as he grasps Keith by the hip to pull him back down against him. “Can I touch you?” Shiro asks, gazing down at Keith’s cock in fascination. To say Keith’s dick is weird might be an understatement. It is prehensile and almost tentacle-like, extending from his body toward Shiro with interest. Keith knows that a full galra’s cock stays sheathed inside his body when not in use, but as a half-galra, Keith has always been different. His partners within the blade were always fascinated by the way the last few inches of Keith’s cock would stay out all the time, positive that it must be causing him pain in some way. 

When Keith was younger he just thought this was the difference between being a grower and being a shower. He was just a grower is all. Perfectly normal. The tapered head was a little odd, but the additional bit of control he had could be attributed to pure talent. All that changed when he hit his second puberty in the quantum abyss. If he thought his first puberty was weird, it was nothing compared to the second. A little bit of extra control turned into a full range of motion, and the bit of growing he was able to do before quickly turned from a couple extra inches to over a foot.

“Yeah, of course,” Keith says. Shiro grins and moves his hand between Keith’s legs to stroke along his length, gasping as Keith’s cock ripples and wraps around his wrist as more of it unsheathes until he has finally revealed the whole thing. 

“I think it likes me,” Shiro says, grinning up at Keith as it writhes in his hand.

Keith rolls his eyes, “I like you, that’s all me.”

“I know we agreed to lay down and see where this goes, but I think I know where I want this to go now,” Shiro says, running his hand from the narrow tip toward the wide base, eyes darkening as he realizes his hand can’t quite close around the spongy tissue at the base.

“And where is that?” Keith asks, closing his eyes to enjoy the sensation of being touched.

“I want it inside me.”

Keith shivers. He didn’t expect that. He thought Shiro, like any reasonable human, would shy away. In a best-case scenario he might politely insist on topping. Keith opens his eyes to look for any sign of hesitation, but Shiro is just looking at him hungrily.

Keith feels like the breath has been punched out of him as he is on the cusp of overwhelmed with feelings of love and gratitude that Shiro is not only okay with him, weird alien dick at all, but seems to be genuinely interested and not frightened off at all by his very literal trouser snake. “Okay, yeah, we can do that,” he manages to choke out as he climbs over Shiro and settles between his legs. “Do you have any lube in here?” Keith asks, not wanting to run back to his room for his own bottle, but willing to do it if he has to. Nothing is going to hold him back from giving Shiro what he wants.

Shiro uses his floating arm to slide open his bedside drawer and retrieve a half empty bottle of lube. He hands the bottle to Keith and releases his hold on Keith's cock as he leans back against the pillows. 

Keith follows him down, kneeling between Shiro's spread thighs and bracketing his body with his arms as their kisses turn from gentle to filthy. Keith grasps Shiro's cock with his own as he reluctantly pulls back just long enough to pour lube over his fingers and reach between them, moving by feel to open him up as he continues to stroke Shiro's cock with his own and kiss anywhere he can reach. 

"I can't believe you've been hiding that from me," Shiro says, panting against the pillows as Keith pulls his fingers out and begins spreading the lube over his cock. The bottle isn't going to last long, so if this goes well they're going to have to stock up before round two.

Keith laughs. "I didn't want to scare you off, I know this is a lot to take in."

"Oh, I'm counting on that,” Shiro says, waggling his eyebrows.

Keith facepalms. “You’re such a dork, do you want this to happen or not?” he asks through his laughter. “Seriously though, tell me when it’s enough. You really don’t have to take the whole thing,” he says as he unwraps his cock from Shiro’s and snakes it down to press against Shiro’s hole. The tapered head is narrow and slips in easily as he slowly slides in, pausing to feel for Shiro’s prostate. Once he finds it he rubs against it while continuing to press forward, giving Shiro plenty of chances to tap out.

Shiro spreads his legs further, encouraging Keith to give him more. “I’ve never felt anything like this before, you’re amazing,” he says. 

Keith hits the halfway point and stops, concentrating on rubbing against Shiro's prostate while Shiro adjusts around him.

"Seriously, how did you get so good at that?" Shiro asks, biting back a moan.

"Lots of practice," Keith answers honestly.

Shiro raises an eyebrow at that. He knows as well as anybody that Keith has been single for years now, and while a hookup or two isn't impossible, that hardly qualifies as 'lots of practice.' "When was this?" Shiro asks in confusion.

"The first time I had any real privacy after the war ended, I don't think I left my room for a week," Keith answers sheepishly.

"Wait, you can do this to yourself?" Shiro asks.

"Yeah, that's weird, right?"

"That's hot. You should show me sometime," Shiro says.

Keith reddens. "Yeah, I can do that. Next time?" 

"Next time," Shiro says with a smile, pulling Keith down for a kiss. 

"Let me know when I can move," Keith says as he leans back from the kiss.

"You can move," Shiro says. 

Keith begins to pull out. "Wait!" Shiro says, wrapping his legs around Keith's back to hold him close. "Not like that, I want all of you."

"If you're sure…" Keith says as he gives Shiro what he wants, keeping up a torturously slow pace as he fills him, twisting and curving around each bend deep inside him as he presses forward.

By the time Keith has only a few inches left to go, Shiro is panting through it. The base is easily as big around as his wrist and the cock inside him is already bulging his belly outward from the size of it. Shiro rests his hand on his stomach in awe, feeling Keith from the outside as Keith pauses again to let him adjust before pushing the rest of the way inside.

Once they are fully joined, Keith takes a moment to appreciate the sight in front of him. Even in his best dreams, he couldn't have imagined what it would really be like to see Shiro spread out beneath him, blissed out expression on his face as he rests his hand over the spot where his belly is bulging outward. Keith moves inside of Shiro and watches as the bulge in his stomach moves too. 

He pulls back slightly and gives a short experimental thrust, punching a moan out of Shiro as he lifts Shiro's leg to change the angle and start fucking him, slowly at first, then picking up speed as Shiro babbles praises and urges him forward. 

Shiro is so tight around him that he doesn't think much of it when he begins to catch on Shiro's rim with each thrust as the pressure builds up behind his navel. As Shiro spills untouched between them, Keith pushes through the tight ring of muscle one last time and feels the pressure ease suddenly as though a release valve has been opened, spilling deep inside of Shiro. 

Once he starts it's like he can't stop. He tries to pull back as Shiro winces but quickly realizes he is stuck. Keith looks down and is alarmed to see that the base of his cock is swollen, stretching Shiro further than is probably advisable. At the same time it feels like _something_ is moving down through his cock. It feels like heaven, but his first concern is with Shiro.

"I don't know what to do, this has never happened before," Keith says in a panic.

Shiro winces as he reaches down to feel, and his eyes widen in alarm as he brushes his fingers over the place where they are joined. "I really don't want to have to try to get to the infirmary like this, maybe if you just pull out really slow?"

Keith reaches for the lube bottle to try to add more to help with the slide, and pulls as gently as he can using the mental picture of the two of them attempting an awkward four legged walk wrapped in only a blanket as motivation. There's no way they would ever live that down. By the time Shiro tells him to stop he has made no progress and is just as stuck as ever.

They carefully reposition to lay face to face on their sides. It's a little awkward, but more comfortable than they were before. "Are you okay?" Keith asks, rubbing his hand gently over Shiro's swollen stomach. "This looks uncomfortable"

"I'm okay, I mostly just feel very full," Shiro says. "We should probably try calling someone to see if this is normal and if there's anything we can do."

"Calling my mom will definitely make it go down," Keith says, making a face.

"It doesn't have to be your mom, maybe Kolivan? Or Coran probably knows at least a little bit about Galra biology," Shiro says thoughtfully. 

Keith doesn't like either of those options. "Let's wait fifteen minutes, and if I don't feel any closer to pulling out, I'll call someone."

Luckily for Keith's dignity, it only takes five minutes. After he pulls out his cock slowly slides most of the way inside his body, with the portion that remains external looking almost deceptively human aside from a tapered head and a wider urethra. Even with the differences, if Shiro didn't already know Keith is half-alien it wouldn't be his first thought.

Keith stands up from the bed on wobbly legs and disappears into the bathroom for some towels to clean up the mess. When he returns, Shiro is curled up on his side with a slightly pained look on his face. 

"I'm so sorry, we don't have to do that again, I really didn't expect it," Keith says as he approaches the bed to gently wipe Shiro down with a wet cloth. The sheets should really be changed before they go to sleep, but putting a dry towel over the wet spot is going to have to be enough for now.

"I want to," Shiro says, guiding Keith down into a kiss. "That was amazing, we'll just have to save it for times when I'm off work the next day."

As Keith moves to lay the towel down, he spots something he has never seen before. A squishy, translucent object, the size and shape and texture all remind him of a peeled grape. 

"I felt something strange come out of me, and I think this might be it," Keith says, holding up the object for Shiro to take a look. 

"We should probably look that up later, you should keep it for a reference," Shiro says, shifting positions to try to get comfortable. 

"Are you sure you're okay?" Keith asks, watching as Shiro shifts uncomfortably in the bed. 

"Just a cramp, I'm sure I'll be fine by morning. If you want to help you can warm up my heating pad, it's in the top of my closet."

Keith finds the heating pad and warms it up before returning to the bed to hold him until they drift off to sleep.

In the morning Keith wakes to the sight of Shiro bent double and sweating as he pants through the pain. 

"Okay, I know you wanted to avoid this, but I really think you need to go to the infirmary," Keith says, concern for Shiro's wellbeing now far outweighing the embarrassment of going to the infirmary for a sex related incident.

Shiro reluctantly agrees and Keith helps him change into comfortable clothes for the long walk across garrison property. 

It's a slow walk, but they make it there. Keith has to fight back the urge to just pick Shiro up and carry him, trying to allow him to get through this with at least some of his dignity left intact.

When they call them back, Keith is relieved to see that the doctor on duty is Galra and should have a better idea of what's going on than a human would. 

The doctor looks concerned as Keith and Shiro explain what happened, until Keith pulls the object he found out of his pocket to ask if it might be related to Shiro's pain.

The doctor's face lights up in recognition. "Oh, you should have just told me you egged. Congratulations! It's normal to feel some discomfort while growing a completely new organ. I can write you a prescription for something to take the edge off, but you should feel much better in about a week."

"A new organ?" Shiro asks in alarm.

The doctor raises her eyebrow. "Well where did you think the baby was going to grow?"

Shiro and Keith turn to each other with matching expressions of surprise and horror before turning back to the doctor, who is now looking at them nervously. "You didn't know anything about this, did you?" she says with the nervous laugh of someone who has just realized she has to explain the birds and the bees to two grown men.

Shiro shakes his head no and glances over to Keith, who is completely still with his eyes wide and his jaw hanging open.

“Okay. Um. You've probably noticed that there are a lot of half-galra. We’ve been a space-faring race for so long that it’s actually very uncommon to meet someone whose ancestry can be traced solely back to Daibazaal, and there’s a reason for that. We’re a very fertile species, and we can reproduce with nearly anyone. If an egg is implanted in someone who would usually not be suited for childbearing, it will wall itself off while a womb forms, branching off of whatever organ it was implanted in. The body will usually only accept one egg at a time, so any others will be absorbed or passed.”

“Oh,” Shiro says quietly, not sure what else he can say to that. Keith is clearly still in shock.

“Let me just get you the number of an obstetrician who can go over your options and hopefully explain what’s happening in more detail. I think I have some pamphlets in my office, I’ll be back in a few minutes,” she says, hastily exiting the exam room.

As the door closes Keith shakes himself out of it and grabs Shiro’s hand. “I had no idea that could happen, I’m so sorry. I’ll do anything I can to make it up to you, I promise.”

“It’s okay, really,” Shiro says. “I’ve spent enough time in space that it was probably about time for an alien to lay eggs in me anyway. I’m just glad that alien was you.”

Keith chokes back a laugh. “Shiro! This is serious!”

“I am serious, I would much rather have your kid than some sort of chestburster,” Shiro says with a grin.

“You really want to do this?” Keith asks in surprise.

“I think I do,” Shiro says thoughtfully, surprising himself with his own answer.

The doctor returns with the pamphlets and a prescription for a mild pain reliever and hands them both to Shiro. One of the pamphlets has a name and phone number scrawled on top for a local obstetrician. She wishes them luck as they head out the door to go back home. There is still a lot to talk about, but they’re confident that this decision is one they won’t regret.


End file.
